Ethereum

Have you been using abi.encode() but you actually are not sure what really happens under the hood? 

Here is a hopefully straight forward explanation what abi.encode() really does.

Breakdown of the Encoding Process:

1. uint256 num = 42:

42 in hexadecimal is 0x2A.

ABI encoding requires a 32-byte representation: 0x000000000000000000000000000000000000000000000000000000000000002A.

2. address addr = 0x1234567890123456789012345678901234567890:

The address is already a 20-byte value.

It is left-padded to 32 bytes: 0x0000000000000000000000001234567890123456789012345678901234567890.

3. string text = "Hello, ABI":

First, the length of the string is encoded as a 32-byte value: 0x000000000000000000000000000000000000000000000000000000000000000A (10 bytes for "Hello, ABI").

The ASCII encoding of "Hello, ABI" is: 0x48656C6C6F2C20414249.

This is right-padded to 32 bytes: 0x48656C6C6F2C2041424900000000000000000000000000000000000000000000.

4. Concatenation:
0x000000000000000000000000000000000000000000000000000000000000002A0000000000000000000000001234567890123456789012345678901234567890000000000000000000000000000000000000000000000000000000000000000A48656C6C6F2C2041424900000000000000000000000000000000000000000000

Now what does abi.encodePacked do? Well, it just doesn't do the padding - so use it with caution if you need to decode the data.

Because strings are easily reconstructed from bytes without padding, you can use abi.encodePacked() to concatenate strings.

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When you use abi.encode() the following operations take place:

1. Encoding:
Each data type is converted into a binary format

2. Padding:
The binary data is padded to encode fixed-size data types (such as uint256, address, bool, etc.) to 32-byte (256-bit) chunks and dynamic-sized data types by first encoding the length of the data followed by the actual data (like fixed-sized data)

3. Concatenation:
The encoded values are concatenated to a single byte array.